I've been making modelling upgrade parts that are compatible Hasbro's kre-o line of minifigs. (The parts are also mostly compatible with Lego minifigs, although the chest plates limit arm articulation.)

Anyway, here are some recent photos I've received from customers!

Any of you Transformers fans want to take a guess as to who the parts might resemble if you squint real hard?

Yeah, Kre-o is basically Hasbro's "we're not Lego" brand of building toys.

The mini-figs are mostly compatible with Lego minifigs except for three main differences:
1) the arms and legs attach to ball joints,
2) the waist attaches with a single 4.8mm cylinder instead of two pegs like Lego,
3) a more or less square torso instead of a trapezoid.

I have a custom torso piece in my shop that should let Lego fans use the chestpieces above (it has ports for lego arms and waists, but is square like a kre-o minifig), but I haven't gotten around to testing it yet.